If you have had good growth of pears in past years, and now have a stunted crop, most likely their is some depletion of soil quality.
Lack of pollination could also be a cause for your small pears, so make sure bees are welcomed to your garden. Pears don't send out a large amount of pollen scent, so it's important to attract them by other means.

Here are a few links about care of your pear tree and pruning guidelines.
I would suggest a soil to determine proper fertilizing of your trees.

Here is also a link to help you locate your nearest extension office that can help you with a soil test.